Adenovirus, any virus belonging to the family Adenoviridae. This group of viruses was discovered in the 1950s and includes 6 genera and 47 species (formerly referred to as serotypes) that cause sore throat and fever in humans, hepatitis in dogs, and several diseases in fowl, mice, cattle, pigs, and monkeys. The virus particle lacks an outer envelope; is spheroidal, about 80 nm (1 nm = 10-9 metre) across; is covered with 252 regularly arranged protein subunits called capsomeres; and has a core of double-stranded deoxyribonucleic acid (DNA) wrapped in a protective coat of protein. Adenoviruses develop within the nuclei of infected cells, where they are often observed packed in an apparently crystalline arrangement.

In humans, adenoviruses cause acutemucous membrane infections of the upper respiratory tract, the eyes, and frequently the regional lymph nodes, bearing considerable resemblance to the common cold. Adenoviruses can also cause epidemickeratoconjunctivitis (EKC) and are considered to be responsible for an outbreak of respiratory disease among military recruits in 1997. Like the cold viruses, adenoviruses are often found in latent infections in clinically healthy persons. Of the 47 different adenovirus species, only a few commonly cause illness in humans; it is thus possible to prepare a vaccine against these viruses. Vaccines include a first-generation inactivated vaccine against several adenovirus types and a non-attenuated oral vaccine against adenovirus types 4 and 7. In contrast, there are more than 100 cold viruses, all of which are commonly found as disease agents; this great number makes the development of a vaccine for the common cold virtually impossible.